--- a/dom/canvas/WebGLContext.cpp
+++ b/dom/canvas/WebGLContext.cpp
@@ -952,17 +952,21 @@ WebGLContext::SetDimensions(int32_t sign
     ++mGeneration;
 
     bool disabled = gfxPrefs::WebGLDisabled();
 
     // TODO: When we have software webgl support we should use that instead.
     disabled |= gfxPlatform::InSafeMode();
 
     if (disabled) {
-        failureId = NS_LITERAL_CSTRING("FEATURE_FAILURE_WEBGL_DISABLED");
+        if (gfxPlatform::InSafeMode()) {
+            failureId = NS_LITERAL_CSTRING("FEATURE_FAILURE_WEBGL_SAFEMODE");
+        } else {
+            failureId = NS_LITERAL_CSTRING("FEATURE_FAILURE_WEBGL_DISABLED");
+        }
         const nsLiteralCString text("WebGL is currently disabled.");
         ThrowEvent_WebGLContextCreationError(text);
         return NS_ERROR_FAILURE;
     }
 
     if (gfxPrefs::WebGLDisableFailIfMajorPerformanceCaveat()) {
         mOptions.failIfMajorPerformanceCaveat = false;
     }